I. Field of the Invention
This invention relates generally to food preservation and sweetening, and more particularly to the preservation of blueberries, cherries and similarly constituted fruits.
II. Description of Related Art
Listed below are the prior art patents and disclosure materials of which the applicant is aware:
"Studies of Reversible Compression of Freeze Dried RTP Cherries and Blueberries", U.S. Army Natick Laboratory Technical Report No. 70-52 F1, 1970, Rahman, A. R., Taylor, G. R., Schafer, G., Westcott, D. E. PA1 U.S. Pat. No. 2,899,319, Issued July 30, 1959; "Dehydration of Cherries", Powers, M. J., Norman, J. D. PA1 U.S. Pat. No. 3,356,512, Issued Dec. 5, 1967; "Method of Making Freeze Dried Artificially Sweetened Fruit Products", Lemaire, N. A., Peterson, R. D., Assignors to Kellogg Company, Battle Creek, Mich. PA1 U.S. Pat. No. 3,395,002 Issued July 30, 1968; "Method of Freeze Drying Fruit and Combining With Dry Cereal", Vollines, W. I. Kenyon, R. E., Barnett, S., Bowden, H., Assigned to General Foods Corp., White Plains, NY. PA1 U.S. Pat. No. 3,467,530, Issued Sept. 16, 1971; "Process of Freeze Drying of Blueberries", Scharschmidt, R. K., Kenyon, R. E. PA1 U.S. Pat. No. 3,511,688, Issued May 12, 1970; "Artificially Sweetened Freeze Dried Food", Vollink, W. L., Scharschmidt, R. K., Kenyon, R. E., Assignors to General Foods Corporation, White Plains, NY. PA1 U.S. Pat. No. 3,806,610, Issued Apr. 23, 1974; "Method for Making a Compressed, Freeze-Vacuum-Dehydrated Blueberry Product of Increased Density", Rahman, A. R. PA1 U.S. Pat. No. 4,341,803, Issued July 27, 1982; "Method of Producing Dry Fruit Chip", D. Koshida, K. Sigisawa, J. Majima, R. Hattori, of Japan.
The aforementioned prior art utilizes freeze-drying to reduce the moisture content of the products, i.e., blueberries, cherries and other fruits. Certain patents apply artificial sweeteners by spraying or dipping the fruit before or after freeze-drying. They attempt to produce a low moisture content in the product that would be rehydrated before eating. The following is a discussion of the prior art listed above:
U.S. Pat. No. 2,899,319 discloses a process for the production of dehydrated cherries comprised of sulphited pitted cherries. The process involves freezing the sulphited cherries then dehydrating by vacuum and heating medium to produce a product that can be rehydrated readily in liquids before eating.
U.S. Pat. No. 3,356,512 discloses a process for rapid artificial sweetening of pieces of freeze-dried fruit product, i.e., peaches, that are readily rehydratable. In this patent, the artificial sweetener in a solvent, i.e., water, is applied to freeze-dried fruits which are then dried to a final product with moisture content not to exceed 3%. The patentees acknowledge difficulties and indicate unsuitability of using sucrose to sweeten the fruit before or after freeze-drying.
U.S. Pat. Nos. 3,395,022 and 3,467,530 disclose processes and improvements of a process to manufacture dehydrated fruit, i.e., strawberries, peaches, blueberries and bananas for use with cereal products, such as breakfast food. The fruit product has a very low moisture content, i.e., blueberries 1.5%, and is capable of rapid rehydration in milk within 30 to 180 seconds. These patents include slow/gradual freezing of the fruit to form large ice crystals in the cells to rupture cell walls to facilitate penetration of the artificial sweetener in the fruit.
Ice rupturing detrimentally affects shape and chewiness of fruit. Another destructive method used in these two patents is the cutting or puncturing by pricking of the skin and cellular structure of the blueberry fruit before freeze-drying. This destructive process to fruit skin and walls results in encouraging leaching of the anthocyanins (the blue coloring material) from the blueberries during the rehydration process into the surrounding liquid, i.e., milk or cream, this bleeding is undesirable, which causes an unappetizing color/appearance in the surrounding liquid and cereal.
U.S. Pat. No. 3,511,668 describes a procedure to artificially sweeten freeze-dried foods, i.e., strawberries, blueberries and peaches. The patentees refer to difficulties in adding sugar in solution or dry form to sweeten the fruit to desired level and freeze-drying the product. Thus, their described procedure to sweeten the fruit includes dipping or spraying solutions containing artificial sweeteners on fruit before freeze-drying to a low moisture content of 2-3% to produce a product that reconstitutes in milk or cream in 30-60 seconds. The processing procedure of slow freezing of the fruit product is used in this patent to form large ice crystals to rupture cell walls to enhance penetration of the artificial sweetener. Specifically, blueberry fruits are pricked or pierced to develop holes in the skin and cellular structure of the berry to provide the enhanced penetration.
U.S. Pat. No. 3,806,610 discloses a process for making compressed, freeze-vacuum dehydrated blueberries by sulfiting the fruit, freeze-vacuum dehydrating to a moisture of 0-5%, heating and compressing, under pressure, the dehydrated fruit.
U.S. Pat. No. 4,341,803 discloses a process for making dry fruit chips, i.e., apple, pineapple, muskmelon, apricot, persimmon and papaya for use as snack food. The process entails adjusting sugar content of the sliced fruit particles or pulp, then drying the chips by freeze-drying followed by microwave drying, then vacuum drying until their moisture content is approximately 5%. It is stressed that successive drying in three stages, by freeze-drying, microwave irradiation under vacuum and vacuum-drying are essential for the production of this product. It is also mentioned that if only the freeze-drying stage, out of the three mentioned drying stages, is employed, it is not possible to produce the desired product. The three drying processes are related in that sequence to achieve the purpose of that patent.
The present invention and product overcomes the prior art problems, mentioned above, by controlling the moisture content of the product and its sweetness without damage to the skin of the fruit or cell walls, and retaining therein the natural color and flavor of the fruit, and through minimal residual surface moisture reduces energy usage and through freeze-drying and sudden release of vacuum, collapses the treated fruit providing a product which is different in appearance, enhanced in taste, shelf life, feel and touch in one's hand and palate.